Remove redundant constraint on multiple providers

We can now handle a single provider (with a priority of 100%).  I
don't think we need to handle the case of no providers.

app/main/views/providers.py

@@ -1,7 +1,7 @@
 from datetime import datetime
 from operator import itemgetter
 
-from flask import abort, render_template, url_for
+from flask import render_template, url_for
 from werkzeug.utils import redirect
 
 from app import provider_client
@@ -56,9 +56,6 @@ def edit_sms_provider_ratio():
 
     form = AdminProviderRatioForm(providers)
 
-    if len(providers) < 2:
-        abort(400)
-
     if form.validate_on_submit():
         for provider in providers:
             field = getattr(form, provider['identifier'])